Surface rename of the signed integer family: s1..s64 become i1..i64
(u1..u64, usize, isize unchanged). 'string' keeps the s-prefix arm in
name classification; width parsing moves to the i-prefix arm next to
isize.
Internal TypeId tags follow the surface (.s8/.s16/.s32/.s64 ->
.i8/.i16/.i32/.i64), as do mono-key mangle fragments (ptr_i64,
tu_i64_bool) and all display/diagnostic formatting (i{d}).
Migrated in the same sweep: stdlib + examples + issue repros + FFI C
companions (shared symbol names like ffi_id_i64), expected
stdout/stderr/ir snapshots, specs.md, readme.md, CLAUDE.md/AGENTS.md,
implementation_plan.md, docs/, issue writeups. Vendored stb_image and
historical flow state left untouched.
zig build test: 426/426; examples suite: 595/595.
An `xx <int>` argument to a variadic `format`/`print` (a comptime `..$args`
pack) segfaulted when the call was inside an imported-module function. Root
cause: lowerPackCall lowered each pack arg with whatever self.target_type was
set to from the surrounding context. A bare arg is unaffected (inferExprType
ignores target_type), but `xx <expr>`'s result type IS target_type — so
`format("…", xx i)` inside a `-> string` fn cast the int to `string`,
monomorphized __pack_string, and ABI-coerced the 4-byte int as a 16-byte string
fat pointer → corruption. Inline it worked only because target_type was null
there; the imported-module path left it set.
Fix: save/clear/restore self.target_type around the pack-arg lowering loop. A
pack arg is independently typed — comptime `..$args` auto-boxes to Any; a value
pack takes its declared element/protocol type — never a leftover outer target.
examples/242-xx-any-pack-cross-module.sx (+ companion fmt.sx) is the regression.
issues/0057 marked resolved. Unblocks ERR E3.3 (the trace.sx formatter formats
frames with `xx frame`).
Gates: zig build, zig build test, bash tests/run_examples.sh (279 passed; lone
failure is the user's uncommitted 213-canonical-map pack WIP).
